1. Field of the Invention
The invention relates to methods for decreasing adverse events associated with pirfenidone (5-methyl-1-phenyl-2-(1H)-pyridone) therapy.
2. Description of the Related Art
Pirfenidone is small drug molecule whose chemical name is 5-methyl-1-phenyl-2-(1H)-pyridone. It is a non-peptide synthetic molecule with a molecular weight of 185.23 Daltons. Its chemical elements are expressed as C12H11NO, and its structure and synthesis are known. Pirfenidone is manufactured commercially and being evaluated clinically as a broad-spectrum anti-fibrotic drug. Several pirfenidone Investigational New Drug Applications (INDs) are currently on file with the U.S. Food and Drug Administration. Phase II human investigations are ongoing or have recently been completed for pulmonary fibrosis, renal glomerulosclerosis, and liver cirrhosis. There have been other Phase II studies that used pirfenidone to treat benign prostate hypertrophy, hypertrophic scarring (keloids), and rheumatoid arthritis.
Pirfenidone is being investigated for therapeutic benefits to patients suffering from fibrosis conditions such as Hermansky-Pudlak Syndrome (HPS) associated pulmonary fibrosis and idiopathic pulmonary fibrosis (IPF). Pirfenidone is also being investigated for a pharmacologic ability to prevent or remove excessive scar tissue found in fibrosis associated with injured tissues including that of lungs, skin, joints, kidneys, prostate glands, and livers. Published and unpublished basic and clinical research suggests that pirfenidone may safely slow or inhibit the progressive enlargement of fibrotic lesions, and prevent formation of new fibrotic lesions following tissue injuries.
It is understood that one mechanism by which pirfenidone exerts its therapeutic effects is modulating cytokine actions. Pirfenidone is a potent inhibitor of fibrogenic cytokines and TNF-α. It is well documented that pirfenidone inhibits excessive biosynthesis or release of various fibrogenic cytokines such as TGF-β1, bFGF, PDGF, and EGF. Zhang S et al., Australian and New England J Ophthalmology 26:S74-S76 (1998). Experimental reports also show that pirfenidone blocks the synthesis and release of excessive amounts of TNF-α from macrophages and other cells. Cain et al., Int'l J Immunopharmacology 20:685-695 (1998).
As an investigational drug, pirfenidone is provided in tablet and capsule forms principally for oral administration. Various formulations have been tested and adopted in clinical trials and other research and experiments. The most common adverse reactions or events associated with pirfenidone therapy include gastrointestinal upset, nausea, fatigue, somnolence, dizziness, headache, and photosensitivity rash. Many of these effects can interfere with everyday activities and quality of life. These effects appear to be dose related. The adverse reactions associated with pirfenidone therapy are exacerbated when pirfenidone is administered at these higher doses.
Currently, adverse events following administration of pirfenidone are alleviated by dose reduction or discontinuation of pirfenidone. In a recent study, for adverse events rated Grade 2 or worse, the dosage was reduced in a stepwise manner: from 9 tablets having 200 mg of pirfenidone per day to 6 tablets having 200 mg of pirfenidone per day and 6 tablets having 200 mg of pirfenidone per day to 3 tablets having 200 mg of pirfenidone per day. Azuma, A. et al., Am J Respir Crit. Care Med 171:1040-47 (2005) (“Azuma study”). More specifically, if, after a period of 14 days of observation with reduced dosage, the adverse event persisted or increased, the dosage was further reduced by one more step—from 6 tablets per day to 3 tablets per day. If the adverse event persisted or increased despite reducing the dosage to 3 tablets per day, the study medication was discontinued.
The Azuma study discloses a dose-titration schedule for all patients wherein patients received a 200-mg dose of pirfenidone three times a day for the first two days; then a 400-mg dose of pirfenidone three times a day for the following two days; and then a maximum 600-mg dose of pirfenidone three times a day for the remainder of treatment. Thus, the maximum dose obtained by the Azuma study was only 1,800 mg/day of pirfenidone. Additionally, the dose-titration schedule of the Azuma study reaches the full maximum dosage of pirfenidone after only four days of treatment. There is significant reason to believe that the Azuma dose escalation does not optimally match the rate of dose escalation with the rate at which a patient develops sufficient tolerance to reduce the incidence of adverse events. Thus, there remains an unmet clinical need for a method of administering higher doses of pirfenidone to a patient in a manner that eliminates or minimizes adverse events, such as nausea, vomiting, gastrointestinal upset, drowsiness, dizziness, headache, somnolence, photosensitivity reaction and other undesirable side effects.